The device and the process forming the subject of the invention relate to the manufacture of hollow bodies by the continuous casting of metals or metal alloys. They relate more particularly to the manufacture by continuous casting of hollow metallic bodies of circular cross-section used as blanks for the manufacture of seamless tubes. It is known that, for such manufacture, the hollow bodies used as blanks must exhibit a high quality of internal and external skin.
French Pat. No. 2.519.567 describes a process for the manufacture of hollow metallic bodies by vertical continuous casting in which a liquid metal is introduced continuously into an annular space between an external metal mold cooled by circulation of fluid and an internal mandrel also cooled by circulation of fluid. The metal gradually solidifies in contact with the walls of the mold and of the mandrel, forming a hollow body which is extracted beneath the mold. In an annular zone adjacent to the external surface of the mandrel, the liquid metal is subjected to the action of a moving magnetic field which creates within this metal forces having a vertical component directed from bottom to top which entrain this metal towards the free surface of the metal bath. This patent describes several methods of producing the moving magnetic field according to the invention. In particular, it describes a method of producing this moving magnetic field which involves the use of permanent magnets arranged over a rotating rotor contained within the internal mandrel, this rotor being caused to rotate about its axis.
The following descriptions, figures and examples will help understanding of the characteristics of the process for the continuous casting of hollow bodies and of the method of producing the moving magnetic field described in French Pat. No. 2.519.567 as well as the characteristics of the magnetic rotor for the continuous casting of hollow bodies forming the subject of the present invention.